Fix output.elasticsearch.proxy_disable flag (elastic#27671)

* Fix output.elasticsearch.proxy_disable flag

Rename the output.elasticsearch.proxy_disabled flag to proxy_disable as
that is what the flag appears as under all other settings including
fleet.

* Add pr number to CHANGELOG

x-pack/elastic-agent/CHANGELOG.next.asciidoc

@@ -81,6 +81,7 @@
 - Fix issue with atomic extract running in K8s {pull}27396[27396]
 - Fix issue with install directory in state path in K8s {pull}27396[27396]
 - Disable monitoring during fleet-server bootstrapping. {pull}27222[27222]
+- Change output.elasticsearch.proxy_disabled flag to output.elasticsearch.proxy_disable so fleet uses it. {issue}27670[27670] {pull}27671[27671]
 
 ==== New features
 
@@ -133,4 +134,4 @@
 - Increase Agent's mem limits in k8s. {pull}27153[27153]
 - Add new --enroll-delay option for install and enroll commands. {pull}27118[27118]
 - Add link to troubleshooting guide on fatal exits. {issue}26367[26367] {pull}27236[27236]
-- Agent now adapts the beats queue size based on output settings. {issue}26638[26638] {pull}27429[27429]
+- Agent now adapts the beats queue size based on output settings. {issue}26638[26638] {pull}27429[27429]

x-pack/elastic-agent/pkg/agent/cmd/enroll_cmd.go

@@ -834,7 +834,7 @@ func createFleetServerBootstrapConfig(
 		}
 	}
 	es.ProxyURL = proxyURL
-	es.ProxyDisabled = proxyDisabled
+	es.ProxyDisable = proxyDisabled
 	es.ProxyHeaders = proxyHeaders
 
 	cfg := configuration.DefaultFleetAgentConfig()

x-pack/elastic-agent/pkg/agent/configuration/fleet_server.go

@@ -33,17 +33,17 @@ type FleetServerOutputConfig struct {
 
 // Elasticsearch is the configuration for elasticsearch.
 type Elasticsearch struct {
-	Protocol      string            `config:"protocol" yaml:"protocol"`
-	Hosts         []string          `config:"hosts" yaml:"hosts"`
-	Path          string            `config:"path" yaml:"path,omitempty"`
-	Username      string            `config:"username" yaml:"username,omitempty"`
-	Password      string            `config:"password" yaml:"password,omitempty"`
-	ServiceToken  string            `config:"service_token" yaml:"service_token,omitempty"`
-	TLS           *tlscommon.Config `config:"ssl" yaml:"ssl,omitempty"`
-	Headers       map[string]string `config:"headers" yaml:"headers,omitempty"`
-	ProxyURL      string            `config:"proxy_url" yaml:"proxy_url,omitempty"`
-	ProxyDisabled bool              `config:"proxy_disabled" yaml:"proxy_disabled"`
-	ProxyHeaders  map[string]string `config:"proxy_headers" yaml:"proxy_headers"`
+	Protocol     string            `config:"protocol" yaml:"protocol"`
+	Hosts        []string          `config:"hosts" yaml:"hosts"`
+	Path         string            `config:"path" yaml:"path,omitempty"`
+	Username     string            `config:"username" yaml:"username,omitempty"`
+	Password     string            `config:"password" yaml:"password,omitempty"`
+	ServiceToken string            `config:"service_token" yaml:"service_token,omitempty"`
+	TLS          *tlscommon.Config `config:"ssl" yaml:"ssl,omitempty"`
+	Headers      map[string]string `config:"headers" yaml:"headers,omitempty"`
+	ProxyURL     string            `config:"proxy_url" yaml:"proxy_url,omitempty"`
+	ProxyDisable bool              `config:"proxy_disable" yaml:"proxy_disable"`
+	ProxyHeaders map[string]string `config:"proxy_headers" yaml:"proxy_headers"`
 }
 
 // ElasticsearchFromConnStr returns an Elasticsearch configuration from the connection string.